The present invention relates to anti-spin devices, and more particularly concerns a simple and improved system for automatically braking the spinning one of a pair of power wheels that are driven through differential gearing.
A major problem with the differential gearing commonly employed to drive power wheels of a vehicle, such as a passenger automobile, or truck, or the like, is the fact that all power may be transmitted to that one of the driven wheels experiencing less resistance to rotation. Thus, it may be difficult or impossible to accelerate a vehicle if one of its drive wheels is in contact with a low friction surface, such as sand, mud, ice, or the like, even though the other of its drive wheels has a good frictional engagement with a solid, non-slip surface. In such a situation, application of power to the wheels through the differential results merely in the spinning of the wheel resting on the low-friction surface. Widespread and intensive efforts over a period of many years have resulted in a number of proposed solutions to the problems of wheel skid and spin, some of which are shown in U.S. Pat. Nos. 4,156,547, 2,583,307, 3,288,232, 4,006,417, 4,066,300, 3,599,014, 2,346,175, 3,779,331, 3,586,385, 3,617,099, 3,706,351, 3,130,805, 3,169,595, 3,463,555, 3,264,040, and 3,264,039. These patents, and other proposed solutions, have involved various devices for sensing differential rotational speeds of the driven wheels, and mechanical, hydraulic or electromechanical arrangements for eliminating or minimizing skidding or spinning. Many of the prior patents are concerned with wheel slipping while braking, attempting to avoid wheel lock-up that may cause skidding, but failing to solve the problem of wheel spin upon acceleration. Despite such efforts, a most commonly employed anti-spin mechanism is a non-skip differential that provides only a limited solution to the problem by means of mechanical arrangements within the differential gearing. Other proposed solutions to the wheel spinning problem are not employed and have not been successful for a number of reasons. Prior devices have been complex, costly and difficult to operate and maintain. Where apparatus is in any way connected with the braking of a vehicle, reliability and safety considerations are of the utmost importance. Therefore, devices of the prior art cannot be accepted if they tend to, or are likely to, compromise reliability, safety and maintainability to existing braking systems.
Accordingly, it is an object of the present invention to provide an anti-spin device that eliminates or minimizes problems of the prior art.